1. Field of the Invention
The invention relates to a method and apparatus for chemically treating an acidic water stream. More particularly, the present invention relates to a portable apparatus which can be easily transported to a remote location for treating an acidic water stream with a minimal amount of human supervision. Furthermore, the apparatus uses the energy of the flowing water in the stream to disperse a treatment chemical agent into the acidic water stream.
2. Description of the Prior Art
Acidic water streams have frequently occurred as a result of coal mining operations. The acidic water streams occurred when natural water flowed through mines and piles of waste materials from mines. The flowing natural water dissolves and carries away various compounds when the water contacts the minerals in the mine or mine waste materials. In particular, if the mining operation involves high sulfur coal then the water will dissolve and carry away sulfur compounds. The dissolved sulfur increases the acidity of the water streams.
The resulting highly acidic water streams represent a significant environmental detriment to water quality in areas where mining operations for high sulfur coals occur. When the highly acidic water stream flows into naturally occurring water streams it greatly diminishes or eliminates the ability of that stream to support aquatic life such as fish. In fact, this form of pollution is common in areas of Pennsylvania, West Virginia and Ohio where high sulfur coals are mined, and is evidenced by orange or yellow colored streams and rivers (i.e., the orange and yellow coloring comes from the precipitation of iron sulfates).
As a result of enactment of various environmental statutes, the operators of high sulfur coal mining operations have developed methods for treating acidic water streams that flow from mines and mine waste piles. In particular, these methods conventionally involve collecting the water into large ponds and then treating the pond with treatment chemicals before discharging the treated water from the pond into naturally occurring streams and rivers. One common treatment involves the addition of lime to the pond where the acidic water is impounded. The lime neutralizes the acidity of the water. This method of treatment suffers from the disadvantage of providing poor mixing between the lime and the water in the pond because the pond water is relatively still. Consequently, excessively large amounts of lime are required to neutralize the acidic water in the pond.
Other methods and apparatus have also been used for neutralizing acid mine drainage water. For example, U.S. Pat. No. 3,142,639 generally describes a method for neutralizing acid mine drainage in which the acid mine drainage is transferred to a mixing container, a solid neutralizing agent is fed into the mixing container from a hopper, the acid mine drainage and the neutralizing agent are mixed in the mixing container, and the treated acid mine drainage water is discharged into a settling basin. The apparatus for practicing this method includes a pump for both transferring the acid mine drainage to the mixing container and transferring the neutralized acid mine drainage water to the settling basin. The pump is either electrically powered or powered by an internal combustion engine.
Likewise, U.S. Pat. No. 4,116,834 describes an apparatus which can be used for neutralizing acid mine drainage by feeding lime from a hopper into a lime slurry tank where the lime is mixed with water to form a slurry and then feeding the lime slurry into a mixing tank where the lime slurry is mixed with the water to be treated. The apparatus of this patent includes a motor driven feeder for transferring the lime to the lime slurry tank and motor driven mixers for the lime slurry tank and the mixing tank. These motors are electrically powered.
Other references also describe similar methods for treating a water stream. For example, U.S. Pat. Nos. 1,722,571; 3,456,801; and 3,595,393 generally describe a water treatment method in which a solid treating agent is added to a portion of the water to be treated in a mixing container and then discharged into another body of water.
The methods and apparatus described in these patents for treating water include the step of taking a portion of the water from the body of water to be treated and mixing the treating agent with that portion of the water in a mixing container before discharging the treated portion of the water back to the overall body of water. This mixing step introduces additional mechanical complexity to the apparatus. Moreover, most of these apparatus and methods require an electrical power supply or an internal combustion engine to power various parts of the apparatus. Thus, these conventional methods and apparatus for treating water streams require frequent human supervision due to their mechanical complexity and due to their use of electrical power or internal combustion engines for power.
Consequently, there is a need for improved apparatus and methods for effectively treating acidic water streams from coal mining operations. In particular, such apparatus would be easily portable to remote locations, require no electrical or internal combustion engine power sources, and be mechanically simple to minimize human supervision.